I too read these reviews with puzzlement. I can only conclude that the Observer's reviewers have a number of labels ('pop', 'rock', 'jazz', 'folk' etc.) which they store in a hat. When they are presented with a CD to review they shake the hat, draw out a label at random and stick it on the CD. Most of the musicians that they choose to review are drawn from a small coterie of ultra-trendy (but obscure) British and American 'yoof' who all make the same general sort of 'noise'. Because very few people have ever heard of these 'artists' the reviewers can get away with the random labelling. Occasionally they review music from Mali, Mongolia or Moldova. For these they use the label 'world' - a label which is not stored in the hat.